1. Field of the Invention
The present invention relates to a cement dispersant. More particularly, the present invention relates to a cement dispersant which can impart a proper fluidity to a hydraulic composition such as cement paste, mortar and concrete, and has an excellent effect on the retention of fluidity of the composition.
2. Description of the Related Art
Examples of cement dispersants which have hitherto be used for the purpose of improving the fluidity of a hydraulic composition include salts of naphthalenesulfonic acid/formaldehyde condensates (hereinafter referred to as "the naphthalene compounds"), salts of melaminesulfonic acid/formaldehyde condensates (hereinafter referred to as "the melamine compounds"), and salts of polycarboxylic acids (hereinafter referred to as "the polycarboxylic acid compounds").
Each of these cement dispersants has a problem, though each has an excellent characteristic. For example, the polycarboxylic acid compounds have the problem of significantly retarding the hardening of a hydraulic composition such as concrete while exhibiting an excellent dispersibility. On the other hand, the naphthalene compounds and the melamine compounds are excellent in dispersibility, and hydraulic compositions each comprising one of these compounds are excellent in hardening characteristics. However, such hydraulic compositions have such a problem that they exhibit a large slump loss (i.e., an elapsing reduction in fluidity).
Thus, compounds satisfying all properties required in cement dispersants have not yet been found, and the existing situation is that conventional cement dispersants involve some problems.